The present invention relates to an automobile airbag device. In particular, the present invention relates to an airbag device enclosure lid for an airbag body placed at a specified location behind an instrument panel body. The instrument panel body includes an airbag pop-out area with a lid for airbag expansion.
Referring to FIG. 3, there is shown an example of the prior art which is the type described in Japanese laid open patent number 63-101255. As can be seen by the figure, there is an instrument panel 1 which includes a base 11 of synthetic resin having an airbag pop-out opening 2. A middle layer 12 is formed from a foam body. Middle layer 12 has a coating 13 on its surface. These three layers that include base 11, middle layer 12, and coating 13, are constructed into a single body.
Airbag pop-out opening 2 has an approximate rectangular shape, having three sides of its perimeter formed in base 11 by channel areas 11 a having a thinned thickness and a remaining side 11c. Airbag pop-out opening 2 has a projection 11b, formed in base 11, which lies along each side of thinned area 11a and which projects in a direction towards middle layer 12. Airbag pop-out opening 2 also has a woven cloth 14 inside middle layer 12 and which covers thinned area 11c.
Behind instrument panel 1 opposite to airbag pop-out opening 2, there is placed an airbag device body (not shown). When the airbag is expanded by an inflator which is housed inside the airbag device body, the expansion pressure splits each of the frangible sides of thinned areas 11a. Projections 11b on thinned areas 11a ruptures through middle layer 12 and coating 13, thereby allowing expanding airbag to emerge from behind instrument panel 1. Referring to the lower part of the figure, the airbag expands, using thinned area 11c and woven cloth 14 as a hinge. Airbag pop-out opening 2 opens up, and the airbag expands into the interior of the automobile.
The number of types of materials and the number of production steps needed to make the conventional airbag device in the instrument panel are many because, in the prior art, the cross-sectional structure of instrument panel 1 is made from a combination of three layers. As a result, there is a problem with high cost.
Woven cloth 14 is placed inside middle layer 12 as a reinforcement for thinned area 11c. When foaming material is injected and molded into middle layer 12, the foam expansion ratio is likely to be uneven. Thus there is a problem due to the unevenness of adhesive strength of woven cloth 14 inside middle layer 12.
There is concern for a problem thought inherent to instrument panel bodies formed from a single layer. That is, the problem of deformation of any structures formed from thinning of the single layer. A lid that is formed behind the instrument panel body can be deformed by an impact to or by pressure on the surface of the instrument panel, thereby distorting the lid.